Ok so I'm stumped on this one. Here's what happens and what I've done so far.

1. Coin up game
2. Press Start
3. Game goes into tilt and kicks out ball
4. Plunge ball and once it goes to the outhole the game cycles to the next ball and goes to tilt as soon as the ball is kicked out
5. Game over

What I've done so far.
Tested all tilt switches using switch edge test. All tilt switches operate properly. (slam, bob, ball roll, PF)
Ran switch status test to see if any tilt switches were active. All tested ok.
Isolated the problem to the MPU by removing the switch connectors and shorting out the trough switches to trick the game into thinking there were balls then shorted the credit button to get the game to start and it does the exact same thing with going into tilt.
This leads me to believe it's an issue on the board. I did some reading about faulty resistor packs so I ohmed out the circuit responsible for the tilt switches and everything checked out within spec.
I decided to replace the PIA at U38 thinking maybe it was kinda flaky and that had no impact.
At this point I'm stumped as the switch test looks fine.

Should I just go ahead and order new resistor packs and replace them? I hate shot gunning parts as that's not typically how I do things.
Anyone have any ideas?

Thanks - I went ahead and ordered all the resistor packs listed in the system 11 bulletproofing thread. Figured I might as well replace them if I pull the board out again since it seems like a common failure point. I'll check the voltages tonight.

Replaced all the resistor packs in the bullet proofing thread. Reflowed solder on all headers. Still tilting. I pulled the roms to verify them and I think that's the issue. One of them failed verification. I've got my fingers crossed it erases and lets me reprogram it as I don't have any roms laying around.

Ok so the Rom didn't fix it. It was bad anyway so I guess there was no harm in replacing it. The actual rom chip was faulty so I ended up finding another 27c256 laying around that I used. I'm stumped now.

Yeah I'm sure. I've done a switch test and verified all tilt switches work I've also shaken the crap out of the game. Then I pulled the actual switch connectors and manually started a game with the whole switch matrix disconnected and it still does it. It is definitely something on the board.

Anyone have any ideas on what I should do next?

It happens when the switch matrix is disconnected from the board.

No I'll check that next. I measured the voltage on the MPU and I'm getting 4.9 v. I ordered new caps for the board as they're original and should be replaced anyway. Is 4.9 too low?

5.0v

They tested fine.